The present invention relates to a monitor apparatus for a boiler and to a combustion monitor method suitable for a multi-burner boiler of a large size such as installed at a thermal power plant.
As a device used in a conventional method for monitoring combustion conditions of a boiler, there are known, as shown in FIG. 1, (1) a flame detector mounted at a burner nozzle for detecting a flame, (2) a detector mounted at an exhaust gas outlet or in a flyash conduit for detecting components contained in an exhaust gas, (3) an ITV camera having an explosion-proof structure and mounted at the upper portion of a furnace for obtaining information on the furnace, and so on. The device (1) detects the light-up and light-down of a burner. The device (2) is provided for detecting the exhaust gas components (particularly, such as nitrogen oxides NO.sub.X and unburnt content) to monitor if they excess a limit stipulated by environment regulations. The ITV camera (3) takes photographs of the internal of a furnace to help an operator grasp the combustion conditions.
Such conventional devices mounted at a boiler can achieve respective objectives. However, they are not always sufficient for monitoring a multi-burner boiler as a whole.
Particularly, the flame detector (1), which detects the "light-up" and "light-down" of a flame at the outlet of the burner, may issue an erroneous judgement of "light-down" if a flame is being lifted from the burner nozzle. The operator has been charged with a final decision for such a case. This is because the flame detector basically operates to outlet light-up (ON) and light-down (OFF) signals of a flame only at the outlet of the burner.
The detector (2) for exhaust gas components takes several ten seconds to several minutes in analyzing the exhaust gas (or several times to several days in case of unburnt components in flyash). Since the components are not obtained on a real time basis, the analyzed values can be used only as a reference in estimating the combustion conditions in a furnace.
The ITV camera (3) mounted at the upper portion of a furnace takes photographs of a flame emitted from the burner located opposite to the camera. Since the flame is photographed while it is swirling, the operator must decide the combustion conditions based on experience and intuition. In addition, the ITV camera must be mounted essentially with an explosion-proof structure for safety purpose, resulting in a troublesome work of its maintenance and the like.
To solve the above problems, a combustion control method has recently been developed wherein a furnace is monitored using an image fiber, as disclosed, for example, in U.S. Pat. No. 4,622,922 issued Nov. 18, 1986 and "A COMBUSTION DIAGNOSIS METHOD FOR PULVERIZED COAL BOILERS USING FLAME-IMAGE RECOGNITION TECHNOLOGY" in IEEE 1985. However, if this method is applied to a multi-burner boiler, it becomes necessary to mount an image fiber and a water cooling tube to all the burners, resulting in very high cost and unpractical approach.